1. Field of the Invention
The invention relates generally to a method for manufacturing a semiconductor device and, more particularly, to a method of removing an ion-implanted photoresist which is used as an ion-implantation barrier and changed in properties during ion implantation.
2. Related Technology
Currently, a photolithography process is necessarily used in manufacture of semiconductor devices including memory devices. In the manufacture of the semiconductor device, after forming an etching mask layer pattern via exposure and development processes using a photoresist, various patterns are formed on a semiconductor wafer via an etching process using an etching mask layer pattern. Here, the photoresist is used as the etching mask layer pattern to form the patterns on the wafer, and thus is necessarily removed after forming the desired patterns on the wafer via the etching process. Removal of the photoresist is performed by a typical stripping process such as oxygen plasma ashing, and entails a cleaning process to remove a residue of the photoresist.
Meanwhile, the photoresist is often used once more as an ion implantation barrier instead of being removed even after it is used as the etching mask layer pattern. For example, when manufacturing DRAM, the photoresist is used as the etching mask layer pattern to form a bit line contact hole. Then, the photoresist is used as the ion implantation barrier upon implantation of p-type impurities for an improvement in contact resistance of a gate tungsten layer exposed in a peripheral circuit region. In this case, however, the photoresist is also implanted with the impurities, which can change properties of the photoresist. In particular, in the case of implanting boron ions, complexation occurs on the photoresist to cause the photoresist to remain on the wafer even after stripping and cleaning processes are performed to remove the photoresist. If the residue of the photoresist exists, the contact resistance increases in the contact region, deteriorating electric properties of the device, and particles of the photoresist act as a source to lowering reliability of the device.
Conventionally, in order to remove the ion implanted photoresist, an additional cleaning process is performed using a buffered oxide etchant (BOE) cleaning solution or a SC-1 (Standard Clean-1) cleaning solution after performing the cleaning process using a sulfuric acid peroxide mixture (SPM) cleaning solution. When the additional cleaning process is performed using the BOE cleaning solution, however, there is a problem in that the bit-line contact hole opened for the ion implantation is widened due to loss of an oxide layer in spite of a high removal rate of the photoresist. In addition, when the additional cleaning process is performed using the SC-1 cleaning solution, there is a problem in that the ion implanted gate tungsten layer is attacked by the cleaning solution.